The postmortem diagnosis of magnesium deficiency: studies in an animal model for the human infant.

Weanling rats were studied as a model for the human infant to determine the optimal tissue in which to assess the status of magnesium after death. Control rats were fed laboratory chow or purified diets that provided a surfeit of magnesium and accommodated a normal rate of growth. Other rats were fed diets that resulted in two degrees of magnesium deficiency: one that might result in spontaneous death within one week, and the other, within two weeks. These times may correlate with six months and one year in the human infant, the period during which the sudden infant death syndrome usually occurs. There was no consistent difference between the magnesium concentration found in the vitreous humor, liver, heart, or skeletal muscle of magnesium-deficient and control rats. However, bone accurately reflected the level of dietary magnesium. There was a significant difference between the magnesium concentration of the anterior and posterior halves of the ribs, indicating irregular distribution of magnesium within the bone. Significant differences were found in the magnesium concentrations of different bones from the same animals. Therefore one entire bone, such as the sternum or the rib, should be studied. The need to match control and study subjects for age was apparent.